Leadframe inductors

Abstract

The present invention integrates an inductor into a semiconductor package by integrally forming inductive segments in the leadframe. The inductive segments may be connected directly to a lead of the leadframe, or indirectly to a lead or a bond pad on a semiconductor die via wirebonds to form an inductor. The inductance value for the resultant inductor is typically controlled by the point of contact for the wirebonds or the leads about the inductive segment. The inductance values may also be controlled by the shape and size of the inductive segments. The leadframe may be formed to support multiple inductive segments, and one or more configurations, including those using one or more die flags to support a like number of semiconductor die.

What is claimed is:  
     
       1. A method for forming an inductor in a leadframe of a semiconductor package comprising: 
       a) forming a leadframe comprising a die flag, leads, and an inductive segment;  
       b) mounting a semiconductor die on the die flag;  
       c) coupling the semiconductor die to a first point of the inductive segment using a wirebond; and  
       d) coupling a second point of the inductive segment to one of the leads or the semiconductor die,  
       wherein the inductive segment is thinner than the die flag and the leads such that a bottom surface of the inductive segment is on a higher plane than bottom surfaces of the die flag and the leads and at least part of the inductor is formed between the first and second points of the inductive segment. 
     
     
       2. The method of  claim 1  wherein the step of forming the leadframe comprises forming the leadframe from a unitary leadframe material. 
     
     
       3. The method of  claim 1  wherein the step of forming the leadframe further comprises forming a second inductive segment. 
     
     
       4. The method of  claim 3  further comprising coupling the second point of the inductive segment to a third point on the second inductive segment and coupling a fourth point on the second inductive segment to the one of the leads or the semiconductor die such that part of the inductor is formed between the first and second points of the inductive segment and at least part of a second inductor is formed between the third and fourth points of the second inductive segment. 
     
     
       5. The method of  claim 4  wherein the second point of the inductive segment is coupled to the third point on the second inductive segment using a wirebond. 
     
     
       6. The method of  claim 1  further comprising applying a molding compound for holding the leadframe, the semiconductor die, and the wirebond in place and forming a body for the semiconductor package. 
     
     
       7. The method of  claim 1  wherein the step of forming the leadframe further comprises forming a plurality of die flags. 
     
     
       8. The method of  claim 1  wherein the step of forming the leadframe further comprises forming a plurality of inductive segments. 
     
     
       9. The method of  claim 1  wherein the inductive segment is substantially linear. 
     
     
       10. The semiconductor package of  claim 1  wherein the inductive segment is substantially non-linear. 
     
     
       11. The semiconductor package of  claim 1  wherein the inductive segment has a spiral shape. 
     
     
       12. The method of  claim 1  wherein the second point of the inductive segment coupled to one of the leads, thereby forming the inductor between the one of the leads and the semiconductor die. 
     
     
       13. The method of  claim 1  wherein the semiconductor die includes two bond pads, and the first point of the inductive segment is coupled to one of the two bond pads and the second point of the inductive segment is coupled to a second of the two bond pads, thereby forming the inductor between the two bond pads of the semiconductor die. 
     
     
       14. A method for forming an inductor in a leadframe of a semiconductor package comprising forming a leadframe comprising a die flag, leads, and at least one inductive segment from a unitary leadframe material, forming at least part of the inductor between two points of the inductive segment, coupling each of the two points of the inductive segment to one of the leads or a semiconductor die mounted on the die flag, wherein the inductance for the at least part of the inductor is determined by a distance between the two points and the inductive segment is thinner than the die flag and the leads such that a bottom surface of the inductive segment avoids contact with a surface contacting bottom surfaces of the die flag and the leads. 
     
     
       15. The method of  claim 14  wherein the step of forming the leadframe further comprises forming a plurality of inductive segments. 
     
     
       16. The method of  claim 15  further comprising coupling portions of each of the plurality of inductive segments in series to form a single inductor. 
     
     
       17. The method of  claim 15  further comprising coupling a portion of each of the plurality of inductive segments between one of the leads or the semiconductor die and isolating the portion from one another to form separate inductors. 
     
     
       18. The method of  claim 14  wherein the step of forming the leadframe further comprises forming the inductive segment such that the inductive segment is physically isolated from the die flag within the leadframe. 
     
     
       19. The method of  claim 14  wherein the step of forming the leadframe further comprises forming the inductive segment such that one end of the inductive segment is physically connected to one of the leads within the leadframe. 
     
     
       20. The method of  claim 14  wherein the step of forming the leadframe further comprises forming the inductive segment such that the inductive segment is physically connected between two of the leads within the leadframe. 
     
     
       21. A method for forming an inductor in a leadframe of a semiconductor package comprising: 
       a) forming a die flag, leads, and an inductive segment from a unitary leadframe material to create a leadframe;  
       b) mounting a semiconductor die on the die flag;  
       c) coupling the semiconductor die to a first point of the inductive segment using a wirebond; and  
       d) coupling a second point of the inductive segment to one of the leads or the semiconductor die;  
       wherein least part of the inductor is formed between the first and second points of the inductive segment. 
     
     
       22. The method of  claim 21  wherein the forming step further comprises forming the die flag, the leads, and the inductive segment such that a bottom surface of the inductive segment is on a higher plane than bottom surfaces of the die flag and the leads. 
     
     
       23. The method of  claim 21  wherein the coupling the second point of the inductive segment step comprises coupling the second point of the inductive segment to one of the leads or the semiconductor die using a second wirebond. 
     
     
       24. The method of  claim 21  wherein the forming step further comprises forming the inductive segment such that the second point of the inductive segment is directly connected to one of the leads, thereby performing the coupling the second point of the inductive segment step.